This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2001-278243, filed Sep. 13, 2001, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
This invention relates to a reacting method of raw materials, and in particular, relates to a reacting method for synthesizing a reaction product such as methanol, wherein the reaction of a raw gas such as a synthesized gas is permitted to take place in the presence of a catalyst by making use of a specific reactor.
2. Description of the Related Art
Methanol, for example, is manufactured by enabling a raw gas such as a synthesis gas comprising hydrogen, carbon monoxide and carbon dioxide to undergo the reaction thereof in a reactor filled with a catalyst. On the occasion of this manufacture of methanol, it involves an exothermic reaction.
In this reaction system involving the generation of heat, the catalyst charged inside the reactor is caused to rise in temperature, which deteriorates the activity of the catalyst. Therefore, various kinds of reactors having a specific structure for controlling the temperature rise of the catalyst-packed portion thereof have been developed.
For example, Jpn. Pat. Appln. KOKAI Publication No. 10-277382 discloses a reactor which is capable of effectively cooling the catalyst-packed portion on the occasion of the reaction of a raw gas.
According to the aforementioned publication, the reactor comprises a casing, with two tube plates for partitioning the interior of the casing into three sections, i.e. an upper chamber, a middle chamber and a lower chamber. A partitioning wall is disposed inside the upper chamber of the casing to partition the upper chamber to an unreacted gas supply chamber and an unreacted gas collecting chamber. A plurality of reaction tubes are disposed inside the casing in a manner that the upper and lower ends of each of the reaction tubes are sustained by the two tube plates. A plurality of inner tubes each having a closed lower end are disposed substantially concentrically in each of said reaction tubes. A plurality of central tubes each having an upper end secured to the partitioning wall are disposed substantially concentrically in each of the inner tubes. An annular space (catalyst-packed portion) is surrounded by and interposed between the reaction tubes and the inner tubes.
According to one embodiment (a first method) of the invention disclosed in this Jpn. Pat. Appln. KOKAI Publication No. 10-277382, methanol is synthesized by a process wherein a raw gas for example a synthesis gas comprising hydrogen, carbon monoxide and carbon dioxide is introduced from the raw gas supply chamber via the central tubs into the catalyst-packed portion to synthesize methanol. Further, according to another embodiment (a second method) thereof, methanol is synthesized by a process wherein a synthesis gas comprising hydrogen, carbon monoxide and carbon dioxide is introduced from the raw gas supply chamber via the central tubs into the catalyst-packed portion, and at the same time, another raw gas having a lower temperature than that of the first-mentioned raw gas is directly fed to the raw gas collecting chamber so as to introduce it into the catalyst-packed portion to thereby synthesize methanol.
In a reactor having a structure as mentioned above, the raw gas supply portion is formed into a triple tube structure comprising a reaction tube, an inner tube and a central tube, wherein a synthesis gas for synthesizing methanol for instance is fed via the raw gas supply chamber to the central tube. In this case, by permitting the synthesis gas to flow through the annular passageway surrounded by and formed between the central tube and the inner tube, the catalyst-packed portion charged in the annular space formed between the reaction tube and the inner tube can be cooled. As a result, it becomes possible to effectively prevent the catalyst-packed portion from rising in temperature that may be otherwise caused due to the exothermic reaction of the synthesis gas.
However, according to the first method set forth in the aforementioned publication, as the activity of the catalyst is gradually deteriorated in the latter stage of a synthesis reaction, the cooling effect of the synthesis gas flowing through the central tube of the reactor becomes somewhat excessive. As a result, the temperature of the catalyst layer becomes too low, thereby possibly deteriorating the production efficiency of methanol.
Further, according to the second method set forth in the aforementioned publication, when a catalyst exhibiting high initial activity is employed or when the flow rate of synthesis gas relative to the amount of catalyst is relatively large, for instance, the temperature of the catalyst-packed portion may exceed the permissible range at the initial stage through the middle stage of the synthesizing reaction, thereby possibly resulting in a high deterioration of the activity of the catalyst. To avoid this, it is possible to raise the ratio of synthesis gas to be fed directly to the central tube as compared with the synthesis gas to be fed to a top portion of the annular space formed between the reaction tube and the inner tube, thereby making it possible, due to the cooling effect of the synthesis gas that has been directly fed into the central tube, to control the temperature of the catalyst-packed portion to fall within the permissible range at the initial stage through the middle stage of the synthesizing reaction.
However, at the latter stage of reaction where the activity of the catalyst is caused to deteriorate, the catalyst would be excessively cooled by the synthesis gas flowing through the central tube and the inner tube of the reactor, thereby possibly deteriorating the production efficiency of methanol.
An object of the present invention is to provide a reacting method which is featured in that the feeding system of the raw material (raw gas, for instance) to a catalyst charged in a reactor for executing the reaction of the raw gas is modified in such a manner that the temperature of the catalyst is controlled in conformity with the activity of the catalyst, thereby making it possible to execute a stable reaction of raw gas during the entire reaction period starting from the initial stage up to the latter stage thereof.
According to the present invention, there is provided a reacting method involving an exothermic reaction wherein a reaction of a raw material is executed by making use of a reactor comprising a plurality of triple tubes disposed in a main body of the reactor, each of the triple tubes comprising a reaction tube, an inner tube having a closed lower end and disposed substantially concentrically inside the reaction tube, and a central tube having an open lower end and disposed substantially concentrically inside the inner tube; a catalyst charged in an annular space formed between the inner tube and the reaction tube of the triple tubes; a first supply port formed in the main body of the reactor and communicated with the central tube; and a second supply port formed in the main body of the reactor and communicated with the annular space;
wherein the raw material introduced from the first supply port is fed via the central tube, via the space formed between the central tube and the inner tube and via an upper end of the inner tube into a layer of the catalyst to permit the reaction of the raw material to take place, and that as the activity of the catalyst is gradually lowered, the quantity of raw material to be fed to the first supply port is correspondingly reduced, and the quantity of raw material corresponding to this reduction of raw material is fed from the second supply port to the layer of the catalyst charged in the annular space.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.